1. Field of the Invention
The present invention relates to a camera, particularly a misoperation detecting device for detecting the misoperation of a mechanical member such as the shutter member whose operation is controlled by means of a magnet.
2. Description of the Prior Art
With respect to photographic cameras, it is very important for a photographer, at the time of taking a photograph, to know whether the shutter has operated normally so as to properly expose the film surface. If it is immediately detected that the shutter has not operated normally and the film surface has not been exposed, it would be possible to reset the shutter and take a picture of the same object from the beginning. If, however, the abnormal operation of the shutter is detected too late, it is very often impossible to take a photograph of the same subject. This is particularly so in ordinary camera systems when completely exposed film has been sent to the developing shop and there is a long time between the actual photographing and the completion of prints. Further, even in the case of the self-developing type camera, such as the instant photographic camera now in mode, it is necessary to wait for about three minutes to obtain a visible image after taking a photograph. Thus, if it is detected in three minutes that the shutter has not operated normally, it would be too late to take a photograph of the same object because the object usually changes in the interim. Consequently, it is most advantageous for the photographer to be able to know at the earliest possible moment whether the camera has operated normally or not.
Some of the conventional cameras have been designed so that the photographer can know at the time of taking a photograph whether the shutter has been normally operated so as to expose the film. For example, as is disclosed in the Japanese utility model pubilication No. Sho 52-41636, a light sensing element for sensing the light beam passing through the photographing lens when the shutter is totally opened is provided in the dark box of the camera. A lamp provided in the view finder is lit by means of a detecting device for detecting a current produced in the light sensing element so that the photographer can confirm that the shutter has operated normally. The above mentioned arrangement for the conventional camera, however, not only requires an expensive light sensing element but also a space in the dark box of the camera in which the light sensing element is to be provided.
Further, a method for detecting the operation of the shutter by detecting the counter-electromotive force produced in the shutter holding magnet, which is brought into the nonexcited state, has also been considered. However, by means of this method, the counter-electromotive force, when the magnet is brought into the non-excited state, is detected so that it cannot be determined whether the shutter member has actually operated or not. In particular, even when for some reason the leading as well as the tail shutter curtain start to run at the time of the shutter release, the tail shutter curtain holding magnet is brought into the non-excited state so that a counter-electromotive force is produced in such a manner that a misoperation confirming operation cannot be carried out correctly. Further, the above mentioned method, in which a light sensing element is used, is inconvenient not only because a space is needed but also because only the shutter operation can be detected. This is so since the light is used in such a manner that it cannot be used for the detection of members, whose operation is controlled by means of a magnet, other than the shutter.